(a) Technical Field
The present disclosure relates to an automatic transmission vehicle. More particularly, the present disclosure relates to a planetary gear train for an automatic transmission vehicle, which is capable of implementing nine forward speeds using a minimum number of configurations, improving power transmission performance and fuel efficiency, and improving ease of installation by reducing the length of the planetary gear train.
(b) Description of the Related Art
Recently, increased oil prices have led to highly competitive efforts to enhance the fuel consumption of fossil-fuel burning vehicles.
To improve fuel consumption in automatic transmission vehicles, research has focused on simultaneously providing better drivability and fuel consumption by having more shift stages for the transmission.
Increasing the number of shift stages in an automatic transmission, however, leads to an increase in the number of parts, which leads to higher production costs, higher weight, decreased ease of installation, and decreased power flow efficiency.
Therefore, it is important to develop a planetary gear train for an automatic transmission vehicle having an increased number of shift stages capable of maximizing efficiency using a small number of parts.
An eight-speed automatic transmission has been recently introduced, and a planetary gear train for an automatic transmission enabling more shift stages is under investigation.
An automatic transmission of eight or more shift-stages typically includes three to four planetary gear sets and five to six control elements (frictional elements), and may easily become lengthy, thereby decreasing ease of installation.
Disposing planetary gear sets in parallel or employing dog clutches instead of wet-type control elements is sometimes attempted. However, such an arrangement may not be widely applicable, and using dog clutches may easily deteriorate shift-feel.
In addition, a recent eight-speed automatic transmission typically shows a gear ratio span in a level of 6.5 to 7.5, which may require improvement for better fuel consumption.
Thus, shortening the length of a planetary gear set for an automatic transmission without deteriorating performance will be beneficial.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.